Indonesia sites astride one of the world’s most critical submarine chokepoints. A large share of global trade must pass through the critical Straits of Malacca, and the shallow littoral waters around the Indonesian archipelago. That makes for excellent submarine hunting grounds, but Indonesia has only 2 “Cakra Class”/ U209 submarines in its own fleet, relying instead on frigates, corvettes, and fast attack craft.
South Korea’s Daewoo, which has experience building U209s for South Korea, has been contracted for Cakra Class submarine upgrades. Even so, submarine pressure hulls have inflexible limits on their safe lifetime, due to repeated hydraulic squeezing from ascending and descending. The Indonesians have expressed serious interest in buying 3-6 replacement submarines since 2007, with French, German, Russian, South Korean, and even Turkish shipyards in the rumored mix. Other priorities shoved the sub purchase aside, but a growing economy and military interest finally revived it. South Korea was the beneficiary, but further orders may be in store.